Werner Likussar

Determination of hypericin in herbal medicine products by differential pulse polarography

A differential pulse polarographic method is presented for the determination of total hypericin in phytotherapeutic preparations (drops, tablets and capsules). The polarographic behaviours of hypericin and of pseudohypericin were examined in various buffer systems over the pH range 3.5–10.0. In Britton Robinson buffer:methanol solution (at pH 6.0) the differential pulse polarograms exhibited reproducible peaks at Ep−1.02 V vs silver/silver chloride for hypericin, and at −1.00 V for pseudohypericin. Under these conditions, a plot of peak height against concentration of hypericin was found to be linear over the range 0.5–9.0 µg/mL (r = 0.9994) and 9.0–16.0 µg/mL (r = 0.9987). The polarographic method was applied to the determination of the content of total hypericin (hypericin, pseudohypericin, protohypericin and protopseudohypericin) in herbal medicinal products containing Hypericum perforatum. The precursors protohypericin and protopseudohypericin were converted into hypericin and pseudohypericin, respectively, by subjecting them to artificial light or daylight prior to analysis. Under these conditions, no separation step was required for the polarographic analysis. In order to evaluate the total concentration of hypericin, the standard addition method with hypericin as standard was applied. The relative standard deviation involved in analysing various herbal medicinal products ranged from ±1.9 to 2.9%. Copyright

Structure Investigation and Proton and Carbon-13 Assignments of Digitonin and Cholesterol using Multidimensional NMR Techniques

Digitonin, a spirostanolglycoside from the seeds of Digitalis purpurea L., is a highly haemolytically active saponin. This effect is considered to be based on complex formation between cholesterin and digitonin. Against the background of investigations concerning the interaction between glycosides and membrane components, and the determination of the structure of the digitonin–cholesterol complex, a detailed NMR spectroscopic investigation of thecomplex‐forming compounds was carried out. Assignment of the 1H and 13C spectra of digitonin was made by using one‐ and two‐dimensional NMR techniques (1D TOCSY, 2D TOCSY, HMQC and HMBC); 3D TOCSY–ROESY, 1D ROESY and HMBC experiments provided information about the sequence of the oligosaccharide chain and the position of glycosidations. The precise analysis of the COSY, HMQC und HMBC spectra made the assignment of all proton resonance signals of cholesterol possible for the first time.

2H-Isoindol-4,7-dione durch Addition von Azomethinyliden an 1,4-Benzochinone

SummaryA new approach to the synthesis of 2H-isoindole-4,7-diones is described. Heating α-amino acids with carbonyl compounds generates azomethine ylides through the elimination of water and carbon dioxide. The ylides were captured by quinones forming 2H-isoindole-4,7-diones, 2,3,3a,7a-tetrahydro-1H-isoindole-4,7-diones and 2,3-dihydro-1H-pyrrolo[2,1-a]isoindole-6,9-diones. The structures were established on the basis of spectroscopy (NMR, mass).

Elektrochemische Eigenschaften von 6-Methoxy-2,5-dimethyl-2H-isoindol-4,7-dion, einem antimikrobiell wirksamen Alkaloid ausReniera-Arten

SummaryTo determine the electronaffinity of 6-methoxy-2,5-dimethyl-2H-isoindole-4,7-dione — the first naturally-occurring isoindole alkaloid — the peak potential was measured by DPP.

SYNTHESE UND POLAROGRAPHISCHES VERHALTEN VON 2H-ISOINDOL-4,7-DIONEN

Summary2-Phenylthio-1,4-benzoquinone (1 a) reacts with azomethine ylide AY-A to give 2-methyl-5-phenylthio-2H-isoindole-4,7-dione (4 f). With 2-(N-methylanilino)-5-methyl-1,4-benzoquinone (1 b), the azomethine ylide AY-B undergoes cycloaddition to yield an inseparable mixture of 5a-methyl-8-(N-methylanilino)-2,3,5,5a,9a,9b-hexahydro-pyrrolo[2,1-a]1H-isoindole-6,9-dione (5 bI) and 9a-methyl-7-(N-methylanilino)-2,3,5,5a,9a,9b-hexahydropyrrolo[2,1-a]1H-isoindole-6,9-dione (5 bII). The structures of5 bI and5 bII were established on basis of two-dimensional-NMR-techniques. The mechanism of the cycloaddition of azomethine ylides to 1,4-quinones was studied on basis of cyclovoltammetric investigations. To determine the electron affinity of the isoindoledione derivatives4 a–f and5 a–b the peak potentials were measured by differential pulse polarography (DPP).

Über die verwendung von oxazinen in der analytik : II.Mitteilung. spektralphotometrische bestimmung von jodid und bromid mit nilblau

Zusammenfassung Der Oxazinfarbstoff Nilblau ist zur Bestimmung von Mikromengen Jodid und Brormid geeignet. Die Farbsalze werden in Chloroform extrahiert und spektralphotometrisch bei 626 nm ausgewertet. Das Lambert-Beersche Gesetz ist im Bereich von 0.5 bis 3 p.p.m. Jodid und 1 bis 6 p.p.m. Bromid erfullt. Der Einfluss von Fremdionen wurde untersucht und die Verfahren statistisch gepruft.

Determination of 5-hydroxynaphthoquinones in phytotherapeutic Drosera preparations by differential pulse polarography

A differential pulse polarographic method is described for the determination of three pharmacologically active 5-hydroxynaphthoquinones in Drosera-containing phytomedicines available on the Austrian market. The polarographic behaviours of plumbagin, 7-methyljuglone and droserone were examined in various buffer systems in the pH-range from 3.5 to 10.0. The compounds were reduced in a single reversible peak at the dropping mercury electrode. The differential pulse polarograms of the naphthoquinones showed distinct peaks in sodium acetate/acetic acid buffer:methanol solution, and a plot of peak height against concentration was found to be linear over the range 0.16–30.0 µg/ml for droserone, 0.06–8.0 µg/ml for plumbagin and 0.16–25.0 µg/ml for 7-methyljuglone. The polarographic method was applied to determine the amounts of these naphthoquinones in three Drosera-containing phytomedicines. In one preparation the droserone concentrations, depending on the sample taken, were found to be 6.81 and 5.78 µg/ml, whilst in a second preparation the droserone concentrations were 1.87, 3.67 and 0.51 µg/ml. The content of plumbagin and 7-methyljuglone was lower than the polarographic detection limit (0.4 µg/ml of each). In a third preparation neither droserone, plumbagin, nor 7-methyljuglone were polarographically detectable (<0.2 µg/ml). Copyright

DETERMINATION OF NISOLDIPINE IN FILM TABLETS BY DIFFERENTIAL PULSE POLAROGRAPHY

SummaryA differential pulse polarographic (DPP) method was developed for the determination of nisoldipine in Baymycard® film tablets without interference from excipients. Nisoldipine is reduced at the dropping mercury electrode in a single, irreversible peak. Linearity between the nisoldipine concentration and the peak height was observed in the 5·10−4–10−7M concentration range. The detection limit is 22 ng/ml. The analysis of a series of 10 Baymycard® 5 mg film tablets showed a standard deviation of ±0.115 mg and aSrel of ±2.30%, respectively.ZusammenfassungEine Bestimmung von Nisoldipin in Baymycard® Filmtabletten mittels differentieller Pulspolarographie (DPP) wurde entwickelt, die keine Störungen durch Tablettenhilfsstoffe aufweist. Nisoldipin wird an der tropfenden Quecksilberelektrode in einem einzigen, irreversiblen Peak reduziert. Linearität zwischen Nisoldipinkonzentration und Peakhöhe wurde im Konzentrationsbereich von 5·10−4–10−7M festgestellt. Die Bestimmungsgrenze beträgt 22 ng/ml. Die Analyse einer Serie von 10 Baymycard® 5 mg Filmtabletten ergab eine Standardabweichung von ±0.115 mg, dies entspricht einerSrel von ±2.30%.

REACTIONS OF HYDROXYETHYLAMINO-1,4-BENZOQUINONES WITH 2,4,6-TRIMETHYLBENZONITRILE OXIDE. II

Summary3,4,9a,9b-Tetrahydro-2H-1,2-oxazolo[5,4-h]1,4-benzoxazin-6(6aH)-ons5a–c were obtained by the reaction of hydroxyethylamino-1,4-benzoquinones2a–c with nitrile oxide3. The structures of the cycloadducts were elucidated NMR techniques including inverse longe-range13C,1H-experiments and homonuclear NOE difference spectroscopy.ZusammenfassungBei der Reaktion von Hydroxyethylamino-1,4-benzochinonen2a–c mit dem Nitriloxid3 werden 3,4,9a,9b-Tetrahydro-2H-1,2-oxazolo[5,4-h]1,4-benzoxazin-6(6aH)-one5 erhalten. Deren Strukturen wurden NMR-spektroskopisch — unter Einbeziehung inverser long-range13C,1H-Experimente und NOE-Differenz-Spektroskopie — aufgeklärt.

Untersuchungen über das morpholin-N-dithiocarbonsaure Morpholinium (MDCM) als Reagens in der quantitativen Analytik. VIII

ZusammenfassungKupfer- und Eisenionen reagieren mit morpholin-N-dithiocarbonsaurem Morpholinium (MDCM) unter Bildung gefärbter Chelate. Diese lassen sich im pH-Bereich von 2 bis 6 mit Chloroform quantitativ extrahieren; die Absorptionskurven der Extrakte überlagern sich teilweise. Durch Messung der Extinktionen der reinen Komponenten sowie der zu untersuchenden Mischungen bei zwei verschiedenen Wellenlängen (438 und 510 nm) läßt sich der Gehalt an Kupfer und Eisen bestimmen. Eine Arbeitsvorschrift wird angegeben und die Genauigkeit der Methode an Hand von Testgemischen überprüft und diskutiert.SummaryCopper- and iron ions react with morpholine-N-dithiocarboxylic acid morpholinium (MDCM) with formation of colored chelates. The latter may be extratced quantitatively with chloroform in the pH-range 2–6. The absorption curves of the extracts overlap in part. The content of copper and iron can be determined by measuring the extinctions of the pure components as well as the mixtures to be investigated at two different wave lengths (438 and 510 nm). A working procedure is given and the precision of the method is checked and discussed on the basis of test mixtures.